In recent years, researches have been conducted with increasing vigor to achieve an improved level of high density recording with optical disks. One of obstacles in doing so is that when a recording condition, such as the quantity of a recording light beam projected on the optical disk or the strength of a recording magnetic field externally applied on the magneto-optical disk, changes, the resultant recording marks vary in width (a size measured perpendicular to the track), which obstructs uniform recording and makes it difficult to effect high density recording.
A solution to this problem is disclosed in Japanese Laid-Open Patent Application No. 11-73700/1999 (Tokukaihei 11-73700; published on Mar. 16, 1999; corresponding to U.S. Pat. No. 6,125,085) whereby the quantity of recording light and the strength of a recording magnetic field are controlled. According to this method, a first test pattern is recorded in a specified track (a track where the recording power is to be optimized), before a second test pattern is recorded in an adjacent track using the same quantity of recording light or the same strength of a recording magnetic field as in the recording of the first test pattern. The first pattern recorded in the specified track is then reproduced. The reproduction signal has an amplitude level reflecting cross-talk during reproduction and cross-erase from adjacent tracks. Therefore, an optimum quantity of recording light or strength of a recording magnetic field can be specified based on the amplitude level of the reproduction signal.
Japanese Laid-Open Patent Application No. 10-69639/1998 (Tokukaihei 10-69639; published on Mar. 10, 1998) discloses a method of recording information in both the land and the groove. According to the disclosure, information is erased in a predetermined track and its adjacent tracks on an optical recording medium. Then, predetermined information is recorded in these adjacent tracks with various recording powers. Subsequently, information in the predetermined track is reproduced to detect the levels of reproduction signals. The levels of reproduction signals are matched to respective recording powers. The recording power at which the level of the reproduction signal shows a sharp increase is designated as the optimum recording power for the predetermined track.
Japanese Laid-Open Patent Application No. 10-69639/1998 describes in its fifth embodiment, paragraphs [0071] to [0073], how to find out the optimum recording power in-both the land and the groove. For example, to obtain a recording power for the land, a signal is recorded in the groove followed by replay of the land to find out a recording power at which the levels of the reproduction signal shows a sharp increase and designate that recording power as the optimum recording power for the land.
However, according to the method disclosed in Japanese Laid-Open Patent Application No. 11-73700/1999 mentioned above, to find the optimum quantity of recording light and strength of a recording magnetic field for the specified track, cross-talk is used which occurs during reproduction in the specified track (the track where the recording power is to be optimized). This shows how the specified track is affected by the recording in the adjacent tracks, not how the adjacent tracks are affected by the recording in the specified track.
Therefore, if recording sensitivity differs between the specified track and its adjacent tracks, the method fails and it becomes impossible to optimize the quantity of recording light and strength of a recording magnetic field.
The same problem exists in the method disclosed in Japanese Laid-Open Patent Application No. 10-69639/1998: it is detected through reproduction in the specified track how the specified track (the track where the recording power is to be optimized) is affected by the recording in the adjacent tracks, and the results will be used to obtain an optimum recording power for the specified track. Accordingly, if recording sensitivity differs between the specified track and its adjacent tracks, the method fails and it becomes impossible to optimize the quantity of recording light and strength of a recording magnetic field.